Fix crash caused by own commit to optimize out curvemapping

initialization. In sculpt mode, when using shift-click to switch to the
smooth brush it was possible to ommit initialization of curvemapping for
that brush.

source/blender/blenkernel/intern/brush.c

@@ -1022,6 +1022,7 @@ struct ImBuf *BKE_brush_gen_radial_control_imbuf(Brush *br)
 	int half = side / 2;
 	int i, j;
 
+	curvemapping_initialize(br->curve);
 	texcache = BKE_brush_gen_texture_cache(br, half);
 	im->rect_float = MEM_callocN(sizeof(float) * side * side, "radial control rect");
 	im->x = im->y = side;

source/blender/editors/sculpt_paint/sculpt.c

@@ -70,6 +70,7 @@
 #include "BKE_node.h"
 #include "BKE_object.h"
 #include "BKE_subsurf.h"
+#include "BKE_colortools.h"
 
 #include "BIF_glutil.h"
 
@@ -3771,6 +3772,7 @@ static void sculpt_update_cache_invariants(bContext *C, Sculpt *sd, SculptSessio
 				brush = br;
 				cache->saved_smooth_size = BKE_brush_size_get(scene, brush);
 				BKE_brush_size_set(scene, brush, size);
+				curvemapping_initialize(brush->curve);
 			}
 		}
 	}